The present invention relates to a clock frequency generator for generating a clock of an unified frequency in the case of converting the format of the video signal of the television receiver, in order to obtain the horizontal and the vertical synchronizing signals for the video signal after converting the format, without changing the field frequency and the scanning lines of the standard video signal.
Recently, in the television broadcasting the digital broadcasting service has been started besides the conventional analogue broadcasting service. In the United States, the digital broadcasting by the surface wave has been started since 1998. In Japan, a digital BS broadcast for mainly servicing a high definition video signal will start in 2000.
There are a variety of standards for signal formats which are employed for the digital television broadcast service. For instance, there are an interlace scanning system signal comprising 525 scanning lines and 858 pixels and a progressive scanning system signal comprising the same 525 scanning lines and the same 858 pixels (these two signals will be referred to SD format signals, hereinafter), a progressive scanning system signal comprising 750 scanning lines and 1650 pixels, and a progressing scanning system signal comprising 1125 scanning lines and 2200 pixels (these two signals will be referred to HD format signals, hereinafter).
In the television receiver compatible with the digital broadcasting, a display format will vary in wider ways, such as a way of supplying the various video signals as mentioned above and away of mixing the HD format signal and SD format signal, a way of displaying by using the synchronizing signal for the HD format signal, or a way of adjusting the screen size to display the graphics or character information on the free space.
In order to comply with the various display formats as mentioned above, it is necessary to convert the format of the video signals between the SD format signal and the HD format signal.
However, if it is considered the number of the scanning lines of each signal formats or the field frequencies (59.94 Hz or 60 Hz), it is difficult to convert the format of the signals as described above by using the standard value. An example of it will be shown below.
First, the horizontal synchronizing signal frequency fH and the clock signal CK of the SD format interlacing scanning signal comprised of 858 pixels and 525 scanning lines are given as follows:                                                                         FH                ⁡                                  (                  SD                  )                                            =                              xe2x80x83                            ⁢                                                (                                      field                    ⁢                                          xe2x80x83                                        ⁢                    frequency                                    )                                xc3x97                                  (                                      number                    ⁢                                          xe2x80x83                                        ⁢                    of                    ⁢                                          xe2x80x83                                        ⁢                    scanning                                                                                                                                          xe2x80x83                            ⁢                              lines                ⁢                                  xe2x80x83                                ⁢                in                ⁢                                  xe2x80x83                                ⁢                1                ⁢                                  xe2x80x83                                ⁢                field                            )                                                                          =                              xe2x80x83                            ⁢                              59.94                xc3x97                                  525                  /                  2                                                                                                        =                              xe2x80x83                            ⁢                              15.734                ⁢                                  xe2x80x83                                ⁢                                  (                  KHz                  )                                                                                                                        CK                ⁡                                  (                  SD                  )                                            =                              xe2x80x83                            ⁢                                                (                  1                  )                                xc3x97                                  (                                      number                    ⁢                                          xe2x80x83                                        ⁢                    of                    ⁢                                          xe2x80x83                                        ⁢                    pixels                                    )                                                                                                        =                              xe2x80x83                            ⁢                              15.734                xc3x97                858                                                                                        =                              xe2x80x83                            ⁢                              13.499                ⁢                                  xe2x80x83                                ⁢                                  (                  MH                  )                                                                                        (        1        )            
This is a case in that the field frequency is 59.94 Hz.
Next, the horizontal synchronizing signal frequency fH and the clock frequency CK of the HD format interlace scanning signal comprised of 2200 pixels and 1125 scanning lines are given as follows:                                                                         FH                ⁡                                  (                  HD                  )                                            =                              xe2x80x83                            ⁢                                                (                                      field                    ⁢                                          xe2x80x83                                        ⁢                    frequency                                    )                                xc3x97                                  (                                      number                    ⁢                                          xe2x80x83                                        ⁢                    of                    ⁢                                          xe2x80x83                                        ⁢                    scanning                                                                                                                                          xe2x80x83                            ⁢                              lines                ⁢                                  xe2x80x83                                ⁢                in                ⁢                                  xe2x80x83                                ⁢                1                ⁢                                  xe2x80x83                                ⁢                field                            )                                                                          =                              xe2x80x83                            ⁢                              59.94                xc3x97                                  1125                  /                  2                                                                                                        =                              xe2x80x83                            ⁢                              33.716                ⁢                                  xe2x80x83                                ⁢                                  (                  KHz                  )                                                                                                                        CK                ⁡                                  (                  HD                  )                                            =                              xe2x80x83                            ⁢                                                (                  2                  )                                xc3x97                                  (                                      number                    ⁢                                          xe2x80x83                                        ⁢                    of                    ⁢                                          xe2x80x83                                        ⁢                    pixels                                    )                                                                                                        =                              xe2x80x83                            ⁢                              33.716                xc3x97                2200                                                                                        =                              xe2x80x83                            ⁢                              74.175                ⁢                                  xe2x80x83                                ⁢                                  (                  MHz                  )                                                                                        xe2x80x83            
This is a case in that the field frequency is 59.94 Hz.
By the values of each signal formats as shown above, it is difficult to convert the format of the signal from SD format signal to HD format signal without changing the original field frequency and the number of the scanning lines. However, in the television receiver which is possible to input both SD format signal and HD format signal, it had displayed the image without converting the format of the video signal in the case of being input the HD format signal. On the other hand, in the case of being input the SD format interlace scanning signal, it had displayed the image by converting the format of the video signal into that of the SD format progressive scanning signal. Here, the conversion to the progressive scanning signal is explained in detail in the Laied-open Japanese patent Application Tokkai-Hei 4-157886.
Here, the horizontal synchronizing frequency of the SD format progressive scanning signal differs from that of the HD format signal.
That is, the horizontal synchronizing frequency of the SD format progressive scanning signal is 31.468 KHz, and that if the HD format signal is 33.716 KHz as shown in the above Equation (2). For instance, in the television receiver using the cathode ray tube, it is possible display any video signals as mentioned above by controlling the difference of the horizontal synchronizing frequency by deflection system. However, in the television receiver which does not equipped with the deflection system such as the liquid crystal projection television, it needs the video signal processing to display the images by the same horizontal frequency.
In the conventional television receiver which converts the format of the video signal, it was needed a generator for generating a clock in order to obtain the video signal field frequency and the scanning lines which comply with every formats.
So, the present invention has an object to provide the clock frequency generator for generating a clock of an unified frequency, so as to obtain the horizontal and the vertical synchronizing signals for the video signal after converting the format without changing the field frequency and the number of the scanning lines of the standard video signal.
According to a first aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of an interlace scanning signal comprising 525 scanning lines into that comprising 1125 scanning lines, comprising:
a multiplier for multiplying by a factor of 4740 a horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines;
a frequency divider for dividing by a factor of 2212 the frequency of the signal obtained in the multiplier, in order to obtain a horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the interlace scanning signal comprising 1125 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines in the multiplier.
According to a second aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of an interlace scanning signal comprising 525 scanning lines into a progressive scanning signal comprising 750 scanning lines, comprising:
a multiplier for multiplying by a factor of 4740 a horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines;
a frequency divider for dividing by a factor of 659 the frequency of the signal obtained in the multiplier, in order to obtain a horizontal synchronizing signal for the progressive scanning signal comprising 750 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the progressive scanning signal comprising 750 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines in the multiplier.
According to a third aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of a progressive scanning signal comprising 525 scanning lines into an interlace scanning signal comprising 1125 scanning lines, comprising:
a multiplier for multiplying by a factor of 2370 a horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines;
a vertical synchronizing signal generator for generating a vertical synchronizing signal for the interlace scanning signal comprising 1125 scanning lines from a vertical synchronizing signal for the interlace scanning signal comprising 525 scanning lines and the signal obtained in the multiplier;
a frequency divider for dividing by a factor of 2212 the frequency of the signal obtained in the multiplier, in order to obtain a horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the interlace scanning signal comprising 1125 scanning lines from the horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines in the multiplier.
According to a fourth aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of a progressive scanning signal comprising 525 scanning lines into that of 750 scanning lines, comprising:
a multiplier for multiplying by a factor of 2370 a horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines;
a frequency divider for dividing by a factor of 1659 the frequency of the signal obtained in the multiplier, in order to obtain a horizontal synchronizing signal for the progressive scanning signal comprising 750 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the progressive scanning signal comprising 750 scanning lines from the horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines in the multiplier.
According to a fifth aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of an interlace scanning signal comprising 525 scanning lines into that comprising 1125 scanning lines, comprising:
a multiplier for multiplying by a factor of 2212 a horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines;
a first frequency divider for dividing by a factor of 5/2 the frequency of the signal obtained in the multiplier;
a second frequency divider for further dividing by a factor of 948 the frequency of the signal obtained in the first frequency divider in order to obtain a horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the interlace scanning signal comprising 525 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines in the first frequency divider.
According to a sixth aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of a progressive scanning signal comprising 525 scanning lines into an interlace scanning signal comprising 525 scanning lines, comprising:
a multiplier for multiplying by a factor of 2212 a horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines;
a frequency divider for dividing by a factor of 4740 the frequency of the signal obtained in the multiplier in order to obtain a horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the progressive scanning signal comprising 525 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 1125 scanning lines in the frequency divider.
According to a seventh aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of a progressive scanning signal comprising 750 scanning lines into a interlace scanning signal of the 525 scanning lines, comprising:
a multiplier for multiplying by a factor of 1659/5 a horizontal synchronizing signal for the progressive scanning signal comprising 750 scanning lines;
a frequency divider for dividing by a factor of 4740 the frequency of the signal obtained in the multiplier in order to obtain a horizontal synchronizing signal for the interlace scanning signal comprising 525 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the interlace scanning signal comprising 525 scanning lines from the horizontal synchronizing signal for the interlace scanning signal comprising 750 scanning lines in the frequency divider.
According to an eighth aspect of the present invention, a clock frequency generator for a television receiver capable of converting a signal format from that of a progressive scanning signal comprising 750 scanning lines into that comprising 525 scanning lines, comprising:
a multiplier for multiplying by a factor of 1659 a horizontal synchronizing signal for the progressive scanning signal comprising 750 scanning lines;
a frequency divider for dividing by a factor of 2370 the frequency of the signal obtained in the multiplier in order to obtain a horizontal synchronizing signal for the progressive scanning signal comprising 525 scanning lines; and
a clock generator for generating a clock which is used for generating the horizontal and the vertical synchronizing signals for the progressive scanning signal comprising 525 scanning lines from the horizontal synchronizing signal for the progressive scanning signal comprising 750 scanning lines in the frequency divider
According to each of the first to eighth aspects of the present invention, the clock frequency generator for the television receiver capable of converting the format of the video signal is possible to generate the clock of the unified frequency to obtain the horizontal and the vertical synchronizing signals after converting the format, without changing the field frequency or the number of the scanning lines of the standard video signal.
Additional objects and advantages of the present invention will be apparent to persons skilled in the art from a study of the following description and the accompanying drawings, which are hereby incorporated in and constitute a part of this specification.